From Gourmet, December 2007
*1 cup all-purpose flour
*1/2 cup sugar
*1 3/4 teaspoons baking powder
*1/4 teaspoon salt
*3/4 stick unsalted butter, melted
*1/2 cup milk
*1 large egg
*1/2 cup raspberry jam or preserves*Preheat oven to 400°F with rack in middle. Generously butter a 9-inch square or round cake pan.
*Whisk together flour, sugar, baking powder, and salt.
*Whisk together butter, milk, and egg in a large bowl, then whisk in flour mixture until just combined. *Pour batter into cake pan. Dollop jam all over surface, then swirl into batter with spoon.
Make Crumb Topping:
*Whisk together butter, sugars, cinnamon, and salt until smooth. Stir in flour, then blend with your fingertips until incorporated. Sprinkle crumbs in large clumps over top of cake.
*Bake cake until a wooden pick inserted in center comes out clean and sides begin to pull away from pan, about 25 minutes. Cool in pan on a rack 5 minutes.